Mobile apps have a distinctive problem. Most are currently standalone programs that often just converse with an app server run by the company that wrote the app. The apps do not have URL links within them. In general, an app from one company does not interact with an app from another company.
Separately, it is much harder for a search engine, which is optimised to search the Web for webpages, to search arbitrary apps. There is no standard syntax equivalent to an URL or URI to enable this.
To enable such and other functionality in mobile apps has been termed ‘deep linking’ within apps. (The term also has an earlier use that refers to standard web pages and URL links within them. This submission does not use that earlier meaning.)
Major companies have several projects aimed at defining deep links. Facebook Corp. has App Links. Google Corp. has App Indexing and Google Intents. Twitter Corp. has App Cards. Apple Corp. has Apple Extensions. Yahoo has 2 US patents pending. There are also several startups, like Bit.ly, Branch Metrics Corp., Button Corp., Quixy Corp., URX Corp., and Tapstream Corp., each with their own initiatives. The syntax and functionality vary between these company specific efforts.